1. Field of the Invention
The present invention relates to a system, method and apparatus for monitoring the condition of engine lubricating oil, and for detecting contamination and deterioration thereof. More particularly, the present invention relates to an oil monitoring system, method and apparatus including a sensor with multiple electrode pairs, mounted on a flexible non-conductive substrate, for receiving and reflecting a wave signal to monitor the quality and condition of engine oil.
2. Description of the Background Art
Detecting oil contamination and deterioration, in an internal combustion engine, is important in promoting and prolonging the useful life of the engine.
The usable life of motor oil depends on many factors, including the type of oil used, the engine""s condition, ambient operating conditions, vehicle usage, and vehicle servicing. While most car manufacturers recommend changing the engine oil of an automobile at three months or three thousand miles, whichever comes first, many automobile owners and operators fail to regularly change the engine oil of their automobile within the recommended time frame.
Where deteriorated oil is subject to prolonged use because of infrequent oil changes, the useful life of an automobile engine is greatly reduced. The useful life of an automobile engine may also be reduced by the introduction of contaminants in the engine oil such as: water, antifreeze, or improper types of oil (e.g. four-stroke oil in a two-stroke engine). Accordingly, some types of oil monitoring methods and equipment, for detecting deterioration and contamination of engine lubricating oil, have been created.
Some examples of sensors for monitoring the condition of engine lubricating oil are illustrated in U.S. Pat. Nos. 4,733,556; 5,274,335; 5,789,665; and 5,929,754.
U.S. Pat. No. 4,733,556 issued to Meitzler et al. discloses an on-board sensor system which compares the dielectric properties of oil within an engine to the dielectric properties of unused oil contained in a sealed area, where both samples experience the same thermal cycling. As the engine oil is circulated through the engine, the on-board sensor continually compares the viscosity of the engine oil to the viscosity of a reference sample of oil, sealed in a container mounted between the engine block and the oil filter. When the viscosity of the two oils differ to a degree greater than a predetermined amount, the on-board sensor system signals that the engine""s lubricating oil need be changed. The sealed oil is similar to the cycled oil, and hence is subject to the same thermal changes in viscosity. In the system of Meitzler et al., the detection of deteriorated oil may be skewed or delayed since the cycled oil is compared to potentially deteriorated oil in the sealed container. Additionally, this approach of monitoring oil quality does not quantify the actual effects of the oil, especially when oil is overstressed by abnormal engine operating conditions.
U.S. Pat. No. 5,274,335 issued to Wang et al. discloses an oil sensor system for detecting engine oil deterioration and contamination. This system involves a method of analyzing engine oil, and detecting oil viscosity and/or contamination, through the use of a dielectric monitoring apparatus, which measures the waveform between two closely placed electrodes (positioned 0.006 to 0.002 inches apart). The electrodes receive and retransmit a wave signal, which transfers information to an on-board monitoring station. When the system receives a signal having a value outside of a predetermined range, the internal sensor relays a message to an in-dash display, indicating the need for an oil change. This sensor system operates through dedicated hardwire implementation, in which the sensor probe is mounted in the engine""s crankcase, and is in direct contact with the oil therein, to read the condition of the oil. As a practical matter, the installation of this type of dedicated hardwire implementation is only feasible during original engine assembly. In addition, since the design of Wang et al. uses only a single pair of electrodes, if there is any problem with this single pair of electrodes, the sensor will be rendered inoperable.
Since this sensor is located inside the engine crankcase, in the event of a sensor failure in the field, sensor replacement is a complex and difficult job, and probably can only be done by a dealer or specialist. The internal location of the sensor increases the difficulty and the cost of maintaining or repairing the sensor.
U.S. Pat. No. 5,789,665 issued to Voelker et al. discloses an engine oil deterioration sensor, which incorporates polystyrene resin beads impregnated with charged ions. The Voelker et al. invention includes an oil sensor attached to the oil pan, as a component of the oil drain plug, thereby utilizing another in-situ method of detection. The sensor housing contains three chambers, and a wire mesh divider is located between each chamber. As the oil deteriorates, the resin beads begin to shrink, and fall through the first wire mesh into the middle chamber. As the oil deteriorates further, the resin beads shrink further, and eventually fall through the second wire mesh lining into the third chamber, which triggers the warning sensor.
U.S. Pat. No. 5,929,754 issued to Park et al. describes a method for determining the minimum lubricating oil thickness within an operating engine, by measuring electrical capacitance of the engine oil. This measurement is calculated by determining the dispersion of an electrical signal as it travels from one electrode through the engine oil to another electrode. The electrode sensing section of the Park et al. invention is partially contained within a cylinder positioned inside the engine, providing in-situ detection. As the oil circulates through the engine, a portion of the oil also cycles through the cylinder via small ports within the cylinder wall. The Park et al. invention is located in on the engine similar to the Wang et al. device, in that it is bored into the engine block, which makes the Part et al. device available only on new cars during production and requires specialized repair and maintenance when the device wears.
While the known devices have shown some utility for their intended purposes, a need still exists in the fluid monitoring art for an apparatus that measures engine lubricating oil quality, through an in-situ system, without requiring specialized repair and maintenance. An oil-quality sensor is needed that can be serviced or changed by non-expert service personnel or by a vehicle owner or, if desired, when the device wears. In particular, there is a need for an oil-quality sensing device combining in-situ monitoring and detection with retro-fit capability, so that the system may be installed on vehicles currently in service.
The present invention has been developed to overcome limitations and disadvantages of known engine oil quality sensors, and to provide a cost-effective, reliable oil quality sensor.
The present invention provides a system, method and apparatus for sensing the condition of oil flowing through an operating oil filter. A sensor apparatus according to the invention may be incorporated into an oil filter assembly.
In accordance with a preferred embodiment, a system according to the present invention provides a multi-electrode sensor on a shape-conforming polymer thick film (PTF), a force-functioning waveform, a potentiostat circuit, and a waveform comparator.
Accordingly, it is an object of the present invention to provide a method and apparatus for detecting oil contamination and deterioration through in-situ monitoring and analysis.
In-situ monitoring offers a superior method of detection, as it monitors the actual oil circulated through the engine. However, proper location of the in-situ device is important for accurate monitoring, i.e. the sensor should be located in a spot where oil is actively circulated, rather than in a xe2x80x98dead spotxe2x80x99 (a location with little or no flow). The highest cycling area of engine oil is within or near the oil filter, and accordingly, the present invention incorporates in-situ detection using a sensor which is made part of the oil filter.
Such an in-situ oil monitoring device is advantageous because incorporation of the sensor into an otherwise conventional oil filter permits the inventive system to be retrofitted to any car, rather than limiting application to new cars only. This capability permits vehicle owners of all makes and models to reap the benefits of oil quality monitoring, which preserves life of their vehicles"" engines. Incorporating the sensor into the oil filter also affords a cost-effective method of oil monitoring, as it requires no specifically designated mounting area and no separate maintenance; a worn sensor is removed and replaced as part of a new oil filter, during an oil change.
Another object of the present invention is to provide a flexible polymer thick film (PTF) as a component of the sensor. A printed sensor pattern on a polymer film permits sensor to conform to the shape of the surface into which it would be integrated, which provides for installation in tight locations or between two fitting surfaces where conventional sensors cannot fit. As a result, the sensor is capable of fitting on an tapping plate of an otherwise conventional oil filter.
Still another object of the present invention is to provide a sensor having multiple electrode pairs. Equipping the sensor with multiple electrode pairs provides advantages of improved sensor performance over single or double electrode design. Multi-electrode processing is advantageous because each electrode pair acts as an independent sensor element, sending multiple independent signals to the monitoring device which then relays an xe2x80x9caveragedxe2x80x9d sensor signal output. The signal-averaging approach potentially reduces operational electromagnetic interference (EMI) noise, which improves the signal-to-noise ratio of the sensor system. The multi-electrode design will also provide some redundancy support that increases system reliability.
Yet another feature of the present invention, due to its multi-sensor capability, is its ability to detect other types of fluids such as contaminated water, de-ionized water, antifreeze, and chlorinated solutions. For example, if an antifreeze leak condition occurs in an engine, the conductivity characteristics or antifreeze would serve as a unique marker with conductivity signature properties different from those exhibited by pure oil. The sensor array is able to detect this condition and provide warning information to a vehicle operator.
For a more complete understanding of the present invention, the reader is referred to the following detailed description section, which should be read in conjunction with the accompanying drawings. Throughout the following detailed description and in the drawings, like numbers refer to like parts.